New Laser Tracking System For Space Debris - Part 1 of 2 Parts

New Laser Tracking System For Space Debris - Part 1 of 2 Parts

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Department of Physics and Astronomy, Purdue University

Part 1 of 2 Parts
      I have blogged before about space junk. There is a huge shell of debris surrounding the Earth left over from decades of the space race. More than half a million pieces are being tracked by radar. These pieces are the size of a baseball or larger. There are millions of pieces that are too small to track with current technology. This junk is whizzing around the world at over twenty-two thousand miles per hour. At that speed, even a bolt can put a hole in a spacecraft.
     There have been predictions that if we do not find a way to diminish the amount of junk accompanying a launch and/or remove the junk already in orbit, the day may come when it is no longer possible to get a spacecraft into orbit without it being riddled by the debris in orbit. One major concern is that if the pieces of space junk collide with each other, they may start a chain reaction of collision and multiplication of fragments.
     More satellites are being launched every year. There are only a couple thousand operational satellites in orbit now but there are plans to launch tens of thousands of satellites in the near future.
     The current way that space junk is being tracked is with radar or lasers. Lasers can be bounced off bits of debris and the returned light analyzed to measure the distance to the object. Earth ground crews can measure how long that it will take them to get where they are going and alert the crew to possible collisions with pieces debris. This laser tracking approach has been used for tracking operation satellites for years.
     Carolin Frueh is an astrodynamics expert at Purdue University. She said, “… with tracking space debris, the situation is different (than tracking satellites). Space junk doesn’t stay in a stable orbit. It will start to tumble and pick up potentially rapid attitude motion, so it is not well oriented.” Laser detections will appear a lot more random for space debris that for satellites. More continuous observations are needed to really predict where the debris is going.
      Laser ranging can only give you a location window that is up to several thousand miles in distance. In order to obtain better predictions, debris trackers can also measure the reflection of sunlight which allows analysts to narrow the window to a few yards. However, these sunlight reflections are only observable around dawn or twilight when the ground stations are still in the dark but the satellites are illuminated by the rising sun.
      A new approach to tracking space debris must be found soon if we are to be able to continue to launch spacecraft into Earth orbit and beyond. Beyond tracking, ways must be found to deorbit or burn up space debris. There are a number of research projects about how to do this. Some of these have been tested and more are on the way but none of them have been selected for wide implementation. Regardless of ultimate solutions to the space debris problem, accurate tracking will be critical.
Please read Part 2 next